1. Field of the Invention
This invention relates to an input responsive damper for generating damping force as a function of the magnitude of externally caused rotary movement.
2. Prior Art Background
A damper is known for reducing the speed of a moving member, e.g. a door, by engaging itself with the moving member (the object of damping) by way of a worm which is rotating at a high rate. Dampers of this category may be subdivided into two types: those of a friction damping type which are popularly used for governors of music boxes and those of a non-contact type that utilize induced electromotive force generated by electromagnetic induction. While a damper of the former type has the advantage of being capable of producing strong damping force, it cannot control its damping effect and generates large frictional noise when it is subjected to a large rotary force.
A prior art device of this type is that disclosed in U.S. Pat. No. 4,616,737.
A damper of the non-contact type is realized by providing a combination of a magnet and a stationary member which are rigidly fitted together as well as that of a conductive member and a worm which are also rigidly bound together so as to induce electromotive force by relative rotation of the conductive member and the magnet when the worm is rotated by the rotary movement of the object of damping by way of a worm wheel. It is a well known fact that relative movement of a conductive member and a magnet which are juxtaposed induces electromotive force so that a magnetic flux may be produced in the conductive member to undo any changes taking place in the state of the existing magnetic flux running through the conductive member. Therefore, the damping force generated in a damper of the second type will be increased as the relative speed of the conductive member and the magnet or the rate of rotation of the worm becomes high. On the other hand, the magnitude of the induced electromotive force can be controlled by modifying the surface area of the magnet and the of the conductive member that face each other. Since a damper of this type can generate a damping effect without contacting the object of damping, it is advantageous in terms of low noise and wear-resistivity.